Prior art devices based on charge centroiding techniques such as the resistive anode and wedge strip anode, provide good resolution but suffer from coincidence losses. During periods of intense radiation they generate spurious signals spatially located between two actual photo events. This occurs when their centroiding electronics cannot temporarily resolve multiple photo events. These losses manifest themselves in either false targets or loss of signal and therefore lead to false target detections or decreasing sensitivity of the detector. This behavior may undermine the performance of an application utilizing this type of sensor. The present invention seeks to avoid this behavior since centroiding of individual photo events is not necessary.
U.S. Pat. No. 4,395,636 to Hal O. Anger, et al., entitled "Radiation Imaging Apparatus," describes a radiation imaging system using a charge multiplier and a position sensitive anode for detecting the centroid position of a charge cloud. The apparatus has two dimensional position coordinate readout capability. The apparatus images incident photons, ions, electrons, or nuclear particles, and has a high inherent spatial and linear resolution. The apparatus disclosed includes systems which use the fast response of microchannel plates, position sensitive repetitive strip and wedge region anodes, and preamps to perform scintillation pulse height analysis digitally.
U.S. Pat. No. 4,845,552 to Bruno Jaggi, et al., entitled "Quantitative Light Microscope Using a Solid State Detector in the Primary Image Plane," describes a solid state microscope apparatus for viewing and scanning microscopic objects. The microscope comprises a light source with a condenser and diffusion filter. The image is projected directly, through one high resolution lens (an objective), onto a large two-dimensional CCD-array or similar solid state image sensor located in the intermediate plane of the objective lens. The sensed discrete image is digitized, conditioned and processed in real time and displayed on a high resolution monitor.
U.S. Pat. No. 4,872,051 to Robert H. Dye, entitled "Collision Avoidance Alarm System," describes an apparatus for detecting the presence of any object on a collision course with a platform or vehicle carrying the apparatus and for generating an alarm upon such detection. A wide-angle television system is used for viewing a scene and providing a plurality of electrical signals corresponding to, and representing the spatial distribution of radiation emanating from the scene. The optical sensor used is optionally of a visibles infrared, or ultraviolet type. Consecutive spatial centroids of an object are computed and used in conjunction with an object's extent to establish possibility of collision.
U.S. Pat. No. 5,131,742 to Fred L. Schaff, entitled "Acousto-Optic Spectrometer/Polarimeter," describes a device which allows broad-band imaging, spectroscopy and polarimetry to be performed simultaneously, and through the same optical aperture. The device comprises an acousto-optic spectrometer/polarimeter for analyzing an incident broad-band beam including an acousto-optic tunable filter for separating the incident broad-band beam into a diffracted extraordinary narrow-band beam, a diffracted ordinary narrow-band beam, and at least one undiffracted broad-band beam. The device further comprises three detectors, each respectively positioned to receive at least a portion of the respective beams and provide first, second, and third signals thereon. Means are provided for radio frequency control, and for transducing an acoustic wave in the acousto-optic tunable filter.